Rotary machines are used for a number of purposes, such as rotary internal combustion engines and pumps of various kinds, including compressors. In many of these a stator is provided in which is rotatably mounted a rotor carrying radially movable vanes which cooperate with the inner surface of the stator to form discrete chambers which vary volumetrically as the rotor carrying the vanes rotates within the stator.
For example, U.S. Pat. No. 3,955,540 discloses a rotary, internal combustion engine in which a rotor carrying vanes is rotatably mounted in a housing. The vanes are spring loaded to maintain their outer tips in sliding engagement with the inner surface of the housing and rollers on their inner ends in engagement with a vane race. With this construction the vanes are pressed into engagement with the inside wall of the stator housing and necessarily there are substantial frictional energy losses as well as appreciable wear of not only the vane tips but the wall against which they are pushed into sliding engagement.
U.S. Pat. No. 3,988,083 is directed to a vane type pump in which frictional engagement between the vane tips and the inside wall of the pump casing is eliminated by providing annular, outside races which are engaged by followers associated with the vanes to thereby limit outward movement of the vanes into contact with the inner wall of the casing. Centrifugal forces are relied upon in this construction to position the vane tips closely to the inner wall of the casing and prevent excessive leakage around the vane tips. However, when high internal pressures are encountered they may be sufficient to overcome the centrifugal forces acting on the vanes, and allow the vanes to lift away from the inner surface of the casing and result in substantial leakage around the vanes.